Development of the mammalian secondary palate is a complex and critical process then when perturbed can lead to cleft palate (CP). Clefts of the primary and/or secondary palate are consistently included among he more common congenital anomalies occurring in humans. Children born with a cleft frequently require several different types of services, e.g., surgery, dental/orthodontic care, and speech therapy, all of which need to be provided in a coordinated manner over a period of years in order to obtain successful rehabilitation. Feeding, hearing, and speech problems are common sequelae of CP making this a significant disability particularly for the very young. Even though the combination of cleft lip with/or without cleft palate (CL/P) is more often seen, CP accounts for approximately one-third of all clefting cases and carries an incidence of 3 to 9 per 10,000 live births/year. CP is considered to an etiologically heterogeneous trait with an important genetic contribution. CP can be associated with more than 370 characterized disord4ers, yet in more than 50%^ cases, CP occurs as an isolated trait (non-syndromic). Our long- term objectives focus on understanding the molecular processes that govern mammalian secondary palate formation and on identifying and characterizing those genetic determinants that contribute directly and/or indirectly to the occurrence of CP in humans. The identification of genes responsible for CP in mice will permit characterization of their temporospatial patterns of expression and function activities during normal palatogenesis; and facilitate investigation of any putative roles played by their human counterparts in familial and sporadic forms of CP. We have identified four lines of transgenic mice resulting from recessive insertional mutations that cause non-syndromic CP. FISH analysis revealed the chromosomal localization of the transgene integration sites in three of the lines. The mutant loci map to Chromosome 3 at bands B-C and F3, in lines of OVE270 and OVE1226B, respectively. The transgene complex in the OVE1328 line localizes to Chromosome 4 at band A2. As a prelude to positional cloning strategies that will lead to the identification and characterizing the gene(s) disrupted, we will focus initially on one transgenic line in order to accomplish following specific aims: (1) identify and map the genomic DNA flanking the transgene complex integration site and (2) determine the interval of genomic DNA that in wildtype mice exists between the DNA that flanks the transgene integration site characterized in aim 1.